1. Field of the Invention
The present invention relates to a drive-on rockable vehicle leveling device for raising a vehicle wheel and retaining it in an elevated attitude.
2. Prior Art
A need has long existed for a safe, reliable drive-on wheel elevating device which can be used in uneven, moist or frozen terrain to raise a selected vehicle wheel and retain it in an elevated attitude.
A present day need for such a device stems from the increasingly popular use of camper trailers and self-propelled camper vehicles. It is desirable that these vehicles be leveled when they are parked for a night's camping, both for the comfort of the occupants and to permit proper operation of gravity fed fluid dispensers and other appliances. Many of these vehicles are heavy and when loaded with equipment, personal belongings and people, impose heavy loads on their supporting wheels. The vehicles are often parked overnight in designated rented areas having an uneven terrain. The ground may well be wet or frozen, which conditions make it difficult to safely level the vehicle.
While at least one rockable leveling device has been proposed for use with camper vehicles, it is not well adapted for use on wet or frozen ground surfaces. The leveling device is not provided with lugs for gripping a vehicle wheel or the ground, and is configured such that it presents a relatively steeply inclined surface to a wheel positioned atop the leveler. As a result, the leveler tends to slip out of place both during the procedure of driving a wheel into position atop the leveling device, and after the wheel is atop the leveler. A significant disadvantage of this proposed leveling device is its relatively long length. In experiments conducted with a conventional vehicle, the device was found to wedge itself against the underside of the vehicle's body as one of the vehicle's wheels was driven onto it. The extensive length of the proposed device prevents its being used between tandem wheels and requires that the vehicle move a substantial distance in driving onto the device. The relatively long length of the proposed leveler device results in a relatively heavy, relatively awkward to handle leveler.
Most known rockable leveling devices utilize a ground-engaging surface which has a radius of curvature that is substantially greater than the radius of the wheel to be elevated. This results in a slow rocking action of the leveling device. The rocking action is so slow as to lag behind the movement of the wheel, thereby necessitating that the wheel roll along the drive-on surface a substantial distance to lock the ramp into position. The vehicle must accordingly be moved through a lengthy distance to effect wheel elevation, and the leveling device must either be of excessive length or designed such that when the wheel comes to rest in its fully elevated position, the wheel is parked on a steeply inclined surface.
Prior drive-on rockable levelers typically have drive-on surfaces with radii of curvature that are substantially greater than the radius of the wheel to be elevated. The larger the radius of curvature of the drive-on surface, the less surface contact it will make with the wheel. When a moist or mud-laden wheel is parked on the inclined drive-on surface of such a leveling device, the wheel can slip down the inclined surface jolting the vehicle and, in some instances, propelling the leveling device from beneath the vehicle.
Other proposed levelers have eliminated the drive-on surface and either substituted a two-point contact with the wheel, or provided a boulder-like appliance which must be strapped to the vehicle wheel to prevent slippage as the wheel is rolled to a position atop the appliance. A two-point wheel contact at opposite ends of a rockable jacking device is not practicable for use with heavy present day camper vehicles as it resuls in unduly high stresses on the jacking device. Strap-on jacking devices are also inconvenient and impractical for use in muddy terrain.